Volcanic fly ash and kiln dust compositions and a process for making articles therefrom

ABSTRACT

The present invention relates to a novel composition which is useful for forming construction blocks and encapsulating hazardous materials, a process for producing blocks and encapsulating the material, and blocks made of the material. This composition is a mixture of klin dust or volcanic fly ash and aggregate. The process comprises the steps of (a) blending a dry mixture comprising the kiln dust or volcanic fly ash mixture with water; (b) transferring the blended mixture into a compression zone and (c) compressing the blended mixture in the compression zone to form a brick of the desired size.

This is a divisional of application Ser. No. 07/870,147, filed Apr. 17,1992, now U.S. Pat. No. 5,366,548, which is a Continuation in Part ofapplication Ser. No. 07/725,312, filed Jul. 5, 1991, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a fly ash composition, acompression/encapsulation process for making products thereof, andproducts made therefrom. In particular, the present invention relates toa composition and a process for making fly ash blocks. The fly ashblocks are useful as a construction material and for encapsulatinghazardous waste.

BACKGROUND OF THE INVENTION

The use of coal for the production of electrical energy has always hadan inevitable consequence, the need to dispose of the ash resulting fromcombustion. Fly ash is a non-toxic waste product which is the result ofcombustion in coal fired generating facilities. The present inventionprovides a means of commercializing the ash produced in the combustionprocess by utilizing the fly ash and bottom ash produced in the coalcombustion process to form compressed blocks which are suitable for useas construction materials.

The destruction of waste materials by incineration or combustion hasgained favor in the U.S., despite some adverse public opinion. Thismethod of disposal is generally less expensive than alternatives, andreduces the volume of the waste to be disposed. However, severalproblems exist with current technology. These problems are: (1) heavymetals are not removed and generally remain in the ash; (2) the ashproduced is reactive and unmanageable; (3) particulate matter is presentin the gas stream; and (4) reactant species in the gas stream mayrecombine to form toxic substances. The present invention addressesitems 1 and 2.

The ash produced by waste incineration generally has a low density. Theparticles have a high surface area. These properties make disposal ofthe ash by ordinary means difficult. The high surface area increaseschemical reactivity, and if water contacts the ash, it leaches out theheavy metal contaminants. This results in contamination of the water andcreates a hazard for living organisms, including man.

The compositions, processes and products of the present invention avoidthese problems through the encapsulation of hazardous materials into thefly ash bricks. This disposes of hazardous waste in such a manner as toprevent the hazardous waste from leaching into the environment. Theprocess of present invention incorporates the hazardous materials intoblocks formed of the fly ash composition of the present invention. Theseblocks have advantageous properties and are resistant to leaching.

SUMMARY OF THE INVENTION

The present invention relates to a novel fly ash composition, a processfor the production of fly ash body, a process for the encapsulation ofhazardous materials, and products made of the fly ash material.

One embodiment of the present invention is a pozzoulanic fly ashcomposition. Preferably, said composition comprises a mixture ofpozzoulanic fly ash and bottom ash. A preferred weight ratio of fly ashto bottom ash in this composition is in the range 80% fly ash:20% bottomash to 20% fly ash:80% bottom ash. This composition can contain 0 to 20%by volume of desired additives when the composition is used to formconstruction blocks, or can contain hazardous waste, when used forencapsulation of hazardous waste. The fly ash composition can also beused as a mortar in the construction walls of the brick composition.

An additional embodiment of the present invention is a method for makingconstruction grade bodies of a fly ash material. This process comprisesthe steps of:

(a) blending a dry material with water, wherein said dry materialcomprises a pozzoulanic fly ash, preferably mixed with bottom ash;

(b) transferring the blended material into a compression zone,

(c) compressing the blended fly ash material to form a fly ash body.

A further embodiment of the presently claimed invention is a method forthe encapsulation of hazardous waste. This process comprises inclusionof a hazardous material with the blended dry material in the aboveprocess, and then conducting the process to form a fly ash blockcontaining the encapsulated hazardous materials.

A fourth embodiment of the present invention is a fly ash constructionblock of the present composition.

A fifth embodiment of the present invention is a fly ash constructionblock which possesses ridges, and an interlocking structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the fill stage of the preferred method of conductingthe presently claimed process.

FIG. 2 illustrates the compression stage of the preferred method ofconducting the presently claimed process.

FIG. 3 illustrates an interlocking fly ash block.

FIG. 4 illustrates an interlocking corner block.

FIG. 5 illustrates the experimental set up which was used in Example 16.

FIG. 6 illustrates graphically, the results of the thermal resistancetest from Example 16.

FIG. 7 illustrates the use of the present invention in a landfill toencapsulate hazardous waste.

FIGS. 8 to 11 show the graphical results of compressive strength testsfor blocks which were formed by compressing the fly ash compositionafter allowing it to set for a certain time period.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

When high pressure is applied to a mixture of water, fly ash and,preferably, bottom ash, an accelerated pozzoulanic reaction takes place.The result is a high quality, structurally sound, building material.Building bricks of the highest quality can be fashioned by applyingoptimum pressure to a combination of ingredients with the correctmoisture content.

Fly ash is the ash product which is exhausted through the smoke stackwith combustion gases during coal combustion. Bottom ash is the ashwhich remains in the furnace after coal combustion. Certain grades offly ash were found to possess pozzoulanic (cement-like) behavior.

One aspect of the present invention is a fly ash composition. Thiscomposition is suitable, for example, for forming fly ash constructionblocks, encapsulating hazardous materials, and use as a mortar to bondthe fly ash blocks together. The present fly ash composition comprisespozzoulanic fly ash. The pozzoulanic fly ash can be used alone, but ispreferably combined with bottom ash. The mixture with bottom ash ispreferred because bottom ash acts as a less expensive filler, and itserves the same role that aggregate does in normal cement. However, anyknown aggregate, such as stone and sand, can be used in a compositionaccording to the present invention. Further, shard glass can be used asaggregate. The use of shard glass as the aggregate provides a way toinexpensively and usefully recycle glass containers and objects withoutthe necessity of sorting green, brown and white glass. A preferredpozzoulanic fly ash is C-grade fly ash.

A preferred fly ash to bottom ash weight ratio for the presentcomposition is in the range 80% fly ash: 20% bottom ash to 20% fly ash :80% bottom ash. A most preferred weight ratio of fly ash to bottom ashis 50:50.

The present fly ash composition can, in addition, contain 0 to 20% byvolume of an additive. The particular additive selected for use isdependent on the specific additional properties which are desired in theconstruction block. Suitable additives for addition to the fly ashcomposition include cement, lime, gypsum plaster, polymers, resins,pumice, volcanic ash, sand clay and sand aggregate. The additive isgenerally present when a specific additional property is desired fromthe fly ash brick. For example, ordinary cement can be added to the flyash composition when a longer setting time is desired, as the presenceof the cement slows the curing of the fly ash block. Selection of theappropriate additive for a particular special property is within theskill of the art.

The fly ash composition can be formed into construction blocks using theprocess of the present invention. In addition, the fly ash compositioncan be used to encapsulate hazardous materials.

Kiln dust, which is a byproduct from the manufacture of cement, can beused in place of the fly ash in the present invention to produceconstruction and encapsulation blocks. The composition can contain from100% kiln dust to 15% kiln dust with the remainder of the compositioncomprising known aggregates and additives, including those describedabove. Likewise, volcanic dust can be used in place of the fly ash inthe present invention with the composition containing from 100% volcanicash to 15% volcanic ash with the remainder comprising other materials,such as the additives and aggregates described above. Constructionblocks formed of the present material satisfy all ASTM and UBCrequirements for construction materials. The fly ash blocks haveextremely high structural strength. The blocks also have high thermalinsulation qualities, and extremely good resistance to thermal shock.Thus, the fly ash blocks are excellent for uses where a high degree ofinsulation is required. These uses include the construction of walls instructures located in areas which have extreme climatic conditions, anduse as fire walls. The blocks can withstand repeated freeze/thaw testswhile saturated with water without exhibiting any damage. Further,freezing the saturated brick and then thermally shocking it did notcause any defects to appear in the block.

The process of the present invention provides a method of producingblocks made from a combination of fly ash and bottom ash. The blockswhich are produced using the present process possess superiorproperties, and these blocks meet or exceed all American Society forTesting and Materials (ASTM) requirements for structural building brick.

The present process comprises the steps of:

(a) blending a dry material with water, wherein said dry materialcomprises pozzoulanic fly ash, and preferably comprises a mixture ofpozzoulanic fly ash and bottom ash;

(b) transferring the blended material into a compression zone, which issized such that it contains an appropriate amount of blended material toproduce a fly ash body of desired size;

(c) compressing the blended fly ash material to form a fly ash body.

The dry material is made up of the fly ash composition of the presentinvention, and can include any additives which are suitable for additionto the construction blocks. These additive are added in the amountsnoted above with respect to the fly ash composition.

The addition of water triggers the pozzoulanic action (cement likeaction) of the fly ash in the dry mixture. The pozzoulanic action is theprocess that binds the ingredients into a solid block. The amount ofwater which is blended with the dry material varies depending on theambient temperature and humidity. The amount of water which should beadded to the dry material is between a minimum of 10% to a maximum of20% by weight, relative to the weight of the dry material. If the watercontent is below 10% by weight, the blend will retain a powderyconsistency which will not set properly or compress well. If too muchwater is added, above 20% by weight, the ingredients will have a muddyconsistency and will squeeze through openings in the compression zone. Apreferred amount of water is in the range 13 to 15% by weight of thetotal amount of dry material. A most preferred amount is approximately14% by weight. Variation in ambient temperature and humidity may requireadjustment of the amount of water in order to optimize the brickcomposition. For example, a lower temperature requires a greater amountof water, to increase lubricity. High temperature, high humidityconditions require the addition of a slightly smaller amounts of water.

Suitable pressure ranges for carrying out the compression step of thepresent invention are in the range from 1000 to 2500 psi. A preferredpressure range for the compression step is 1500 to 2500 psi. Aparticularly preferred compression pressure is 1750 psi.

An preferred example of the compression zone is the press box of amultiple ram press, as shown in FIGS. 1 and 2.

FIGS. 1 and 2 illustrate a preferred mode of carrying out the presentprocess and are helpful in illustrating the process steps. A preferredmode of carrying out the process of the present invention is as follows:

(1) A dry material is formed of the presently claimed fly ashcomposition, wherein the fly ash to bottom ash weight ratio is in therange 80% fly ash : 20% bottom ash to 20% fly ash : 80% bottom ash.

(2) After the dry material is formed, it is blended with water, which isadded in an amount which is approximately 14% by weight relative to thetotal weight of the dry material.

(3) The blended material then transferred to the press box, as shown inFIG. 1. The blended material is deposited into the magazine hopper 1.The magazine hopper 1 feeds the magazine 2 which deposits the blendedmaterial 5 into the press box 4 using the magazine ram 3. The amount ofingredients deposited into the press box is dependent on the size of thebrick which is to be formed. The press box 4 is appropriately sized soas to contain the correct amount of blended material which is needed inorder to produce a block of the desired size.

(4) After the press box is filled, compression is conducted to form thefly ash brick, as shown in FIG. 2. During the compression step, theejection ram 6, which forms the bottom surface of the press box 4,lowers from the fill position to the fully depressed position. Then thecompression ram 7 moves to compress the ingredients in the press box.When maximum psi is reached, the compression ram 7 returns to its startposition, and the ejection ram 6 pushes the resulting block out of thepress box.

The fly ash blocks are ready for use immediately upon ejection from theproduction apparatus. Thus., there is no need for an extended curingtime. The blocks can cure in the wall or during storage.

The preferred process of present invention can be carried out, forexample, by using a multiple ram block machine which produces the flyash blocks, as illustrated in FIGS. 1 and 2. The apparatus can either bea fixed site facility, or it can be a mobile facility. For example, theapparatus is suitable for mounting of the truck bed of a goose neck flatbed trailer. This allows the device to be taken to the site where theblocks are needed, and allows the fabrication of blocks on site. Thistype of fabrication reduces the costs of materials transport, as thereis no need to transport finished blocks. Between six and seven blocksper minute can be produced by this apparatus, and blocks which areproduced using the machinery are ready for immediate use. A suitableapparatus for use with the present material and in the present processesis disclosed in the co-pending application by the present inventor,which has been assigned Ser. No. 725,313. The contents of thisco-pending application are hereby incorporated by reference.

An additional embodiment of the present invention is a process for theencapsulation of hazardous materials. This encapsulation process is amodification of the above described process for making fly ash blocks.In the encapsulation process, a hazardous material is blended with thefly ash material to form the dry material.

The present encapsulation process provides a low cost and easily managedmethod for disposal of a variety of hazardous waste materials. Any typeof waste which can be successfully incorporated into the fly ash blockis suitable for use in the present encapsulation process. Specific,non-limiting, examples of hazardous materials which are suitable for usein the present encapsulation process include asbestos, contaminatedsoils, pesticides, herbicides or other toxic or hazardous chemicalcompounds, petroleum waste products, PCB contaminants, low yieldradioactive waste, acids, medical ash, municipal solid wastes,incinerator ash, heavy metals and gasification plant ash.

The maximum amount of hazardous waste which can be encapsulated in theblock varies as a function of the waste material. Encapsulation formulasvary from as little as 25% C-grade fly ash up to 50% c-grade fly ash,depending on the materials to be encapsulated. In addition, bottom ashcan be added in order to increase brick integrity. These conditions arecontrolled by the standards and conditions imposed by the circumstancesin which the brick is used. For example, medical ash can be encapsulatedin an amount as large as 75% by weight, without impairing the structuralintegrity of the brick. Other types of waste, such as oils and petroleumproducts, can be encapsulated at a much lower amount, for example in therange 10 to 20% by weight. Different hazardous materials producedifferent effects on the strength of the brick. The amount of wasteproduct encapsulated should not be high enough to affect the structuralintegrity of the block. This amount can be determined by those skilledin the art without undue experimentation for the particular hazardousmaterial which is to be encapsulated.

The blocks which contain the encapsulated hazardous material are ideallysuited for hazardous material disposal, as they are high strength, arelong lasting, and have low leach rates. Thus, the hazardous materialswhich are encapsulated in the fly ash composition will not leach outinto the ground water. The blocks are also high strength and have a longlife span, on the order of 2000 years. Further, the use of blocks tocontain the encapsulated hazardous waste places the waste in a formwhich is easy to handle, and reduces the total volume of waste which isdisposed. This eases land fill congestion and provides an reliablemethod of hazardous disposal.

Blocks containing the encapsulated hazardous waste can be disposed of inland fills, or can be used in suitable construction projects, such aserosion control walls, levees, breakwaters, etc. When these blocks aredisposed of in land fills, a layer of the fly ash blocks of the presentinvention can be placed below the contaminated blocks as an additionalliner.

FIG. 7 illustrates an example of a type of land-fill disposal for theencapsulated hazardous materials. A layer of fly ash/bottom ash slurryis 9 placed on the bottom and sides of a hole. A layer of uncontaminatedbrick 10 is then placed as a lining. Finally, the contaminated bricks 11are filled into the middle, covered with a layer of uncontaminated flyash brick 10 and sealed with a fly ash/bottom ash slurry 9.

When low grade radioactive waste is the encapsulated hazardous material,the encapsulation process comprises an additional step. In this step, afly ash composition is heated to a temperature sufficient to liquify it.This temperature is approximately 1400° C. The fly ash block containingthe encapsulated radioactive material is then dipped into the liquefiedash composition. The liquified ash composition coats the outside of theblock, and forms a glass coating layer on the outside of the block.Preliminary results show that this glass layer is impervious toradiation. Thus, the glass layer should prevent radiation from theencapsulated waste from escaping into the environment.

A further embodiment of the present invention is a contoured block madeup of the fly ash material. Two types of contoured blocks can be formed,the standard contoured block is illustrated in FIG. 3. The contouredblock contains a ridge 12 which is located down the center axis of thetop face of the block 15. A groove 13 which is the same shape as theridge is located in the center portion of the bottom face, directlybelow ridge 12. The contoured brick is designed so that when the bricksare used to construct a wall, ridge 12 interlocks with groove 13 on theblock above it. The groove 13 is slightly larger than ridge 12 in orderto provide a gap therebetween for mortar, which can be injected into thegap through grooves 14.

FIG. 4 illustrates a corner contoured block. The corner contoured blockhas the advantage that it provides a double interlock feature; ridges 15and 16, on the top face, and grooves 18 and 19 on the bottom face. Thecontours located on the corner brick interlock the adjoining bricks inboth walls. As with the contoured brick shown in FIG. 3, the grooves 18and 19 are slightly larger than the ridges 15 and 16 in order to providea gap therebetween for mortar, which can be injected into the gapthrough the grooves 17.

This interlocking groove system at the corner provides superior bondedand structural strength and provides earthquake resistance due to thedouble interlock feature. In addition, these blocks can be bonded into astructure using a mortar which is made up of the present fly ashcomposition. This allows the construction of structures with hightensile strength, because the composition of the wall is homogenous.

The following examples are intended as illustrations of the use of thepresent invention but are not deemed to limit the scope of the presentlyclaimed invention.

EXAMPLE 1

A standard fly ash brick.

15 lbs of bottom ash and 15 lbs of C-grade fly ash were mixed together.4.2 lbs of water (14% of the total weight of the dry composition) wasblended into the dry fly ash/bottom ash mixture. The resulting blendedmixture was placed into a press box and was compressed to form a blockusing a maximum pressure of 1750 psi.

EXAMPLE 2

Encapsulation of Medical Ash

A fly ash block was formed of 25% C-grade ash and 75% medical waste ash.The dry material was blended with water which was added in an amountwhich was 12% of the combined weight of the dry ingredients. The blendedmaterial was placed in a press box and was compressed to form a blockusing a maximum pressure of 1750 psi.

The water content added was slightly less than that added to thestructural brick in Example 1, as the medical ash is highly absorbent,and as a result, less water is required to optimize compactibility. Thecompaction rate was 60% of the free fall volume.

EXAMPLE 3

Encapsulation of Municipal Solid Waste

A fly ash block was formed of 25% C-grade ash and 75% municipal solidwaste ash. The dry material was blended with water which was added in anamount which was 14% of the combined weight of the dry ingredients. Theblended mixture was placed in a press box and compressed to form a brickusing a maximum pressure of 1750 psi. The compaction rate was 50% of thefree fall volume.

EXAMPLE 4

Encapsulation of Oils Suspended in a Medium, such as dirt, powder,Cinders, etc.

A fly ash block was formed of 33% C-grade ash and 15% oil and 52% of asuspension medium. The oil was mixed with the suspension medium, whichcan include dirt, powder, cinders, lime, etc. The resulting mixture ofoil and suspension medium was mixed with the C-grade fly ash. The drymaterial was blended with water which was added in an amount which was14% of the combined weight of the dry ingredients. The blended mixturewas placed in a press box and compressed to form a brick using a maximumpressure of 1750 psi.

The compaction rate of the blocks formed of this material is dependenton the suspension medium. For example, when lime is used as thesuspension agent, and PCB's are used as the oil in the abovepercentages, the compaction rate is 45%.

EXAMPLES 5 TO 15, COMPARATIVE EXAMPLES 1 TO 4

Fly ash blocks of the present invention (Examples 5 to 15) were formedusing a fly ash/bottom ash ratio as shown in Table 1. In table 1, PA isPawnee Ash, which is C-grade fly ash obtained from the Pawnee ElectricalGenerating Plant, CA is Comanche Ash, which is C-grade fly ash obtainedfrom the Comanche Electrical Generating Plant. These compositions wereblended with water in an amount of 15% by weight. The blended mixturewas placed in a press box and compressed to form a brick using a maximumpressure of 1750 psi. The thickness, compressive strength, modulus ofrupture, and final moisture content of the bricks is shown in Table 1.

Comparative examples 1 to 4 contain red clay or sand clay in addition tothe fly ash and bottom ash. These bricks contain 25% fly ash by weight,25% bottom ash by weight, and 50% by weight of yellow or red clay. Thesedry materials were also blended with water in an amount of 15% byweight, and compressed as above.

The same properties which were tested for the bricks of the presentinvention were also tested for the other bricks. These bricks displayedlower compressive strengths and modulus of rupture, overall, then thoseobserved for the bricks made of the present materials.

                                      TABLE 1                                     __________________________________________________________________________    Examples 5-15                                                                 Cast Into 10" × 14" Bricks                                              PA -- Pawnee ash                                                              CA -- Comanche ash                                                            BA -- Bottom ash                                                                                    Compressive                                                                           Modulus of                                                                            Moisture                                Example                                                                            INGREDIENTS                                                                              Thickness                                                                           Strength                                                                              Rupture Content                                 No.  Measured by Volume                                                                       (Inches)                                                                            (psi) @ 12 days                                                                       (psi) @ 10 days                                                                       (% of dry wt.)                                                                        COMMENTS                        __________________________________________________________________________    5    1/2 PA, 1/2 BA                                                                           3.45  2965    172     2.7                                     6    1/2 PA, 1/2 BA                                                                           4.12  2685     47     3.6     added water                     7    1/2 PA, 1/2 BA                                                                           3.65  1920    291     4.1     #3 & #4 -- same amount of                                                     water                           8    1/2 PA, 1/2 BA                                                                           4.05  5050    258     7.5     #4 would have been a little                                                   dry as                                                                        it set a few minutes                                                          longer.                         9    1/2 CA, 1/2 BA                                                                           3.64  2950    384     4.8                                     10   1/2 CA, 1/2 BA                                                                           3.75  2920    340     4.7     mix set 3 to 5 min. longer                                                    and                                                                           got dryer.                      11   1/4 CA, 3/4 BA                                                                           3.50  2655    178     3.9                                     12   3/4 CA, 1/4 BA                                                                           3.45  3125    173     3.3                                     13   3/4 PA, 1/4 BA                                                                           4.22  2495    215     3.6                                     14   1/4 PA, 3/4 BA                                                                           2.75  3170    265     4.0                                     15   100% PA    3.45  3520    328     6.4                                     Comp.                                                                              1/4 PA, 1/4 BA,                                                                          3.86  1970     9      5.1                                     Ex.  1/2 red clay                                                             Comp.                                                                              1/4 CA, 1/4 BA,                                                                          3.95  1400     95     4.2                                     Ex.  1/2 red clay                                                             2                                                                             Comp.                                                                              1/4 CA, 1/4 BA,                                                                          3.66  1000     51     3.6                                     Ex.  1/2 yellow sand clay                                                     3                                                                             Comp.                                                                              1/4 PA, 1/4 BA,                                                                          3.69  1300     39     4.4                                     Ex.  1/2 yellow sand clay                                                     4                                                                             __________________________________________________________________________

EXAMPLE 16

The heat flow characteristics of the blocks formed of the presentcomposition were tested. The fly ash blocks were made from the followingcomposition: 28% Comanche C-grade fly ash, 30% of a mixture of F-gradefly ash and bottom ash (15% each F-grade fly ash and bottom ash) and 42%bottom ash. 15% water by weight was blended with the dry material, andit was compressed into bricks at 1750 psi. The test procedure consistedof mortaring 4 inch thick bricks to form the structure which is shown inFIG. 5. Type K Chromel-acumel thermocouples were cemented in the cavity,on the rear, and in the frame. A weed burner connected to the outlet ofa 250 lb propane tank was positioned as shown in FIG. 5. The burner facewas six inches from the block assembly face. The results of the test areshown in Table 2, and are depicted graphically in FIG. 6. The burner wasrun for 3 hours, and the temperatures were measured. After 3 hours, theburner was turned off and the temperature was measured for another 3hours. The flame temperature was 2000° F.

The temperature in the cavity was raised 120 degrees over a 3 hourperiod. After the flame was turned off, the temperature droppedslightly, and then remained relatively constant at around 190° F. for 2hours before slowly tapering off.

The temperature at the rear face of the block wall was raised 40 degreeswhile the burner was operated, and went up another 20 degrees.

No evidence of spalling, cracking, checking or other form ofdeterioration was observed on the bricks. In addition, not only did thematerial display excellent resistance to heat gain, but alsodemonstrated slow heat release properties, which would suggest potentialutility as a heat storage medium.

                  TABLE 2                                                         ______________________________________                                        Time     Temperature (F.)                                                     (min)    Flame   Cavity   Rear Face                                                                             Observations                                ______________________________________                                         0       2000     0        0                                                   15      2000     60       60                                                  30      2000     61       60                                                  45      2000     62       60                                                  60 (1 hr)                                                                             2000     78       60                                                  75      2000     93       64                                                  90      2000    115       65                                                 105      2000    143       68                                                 120 (2 hr)                                                                             2000    162       69                                                 135      2000    172       78                                                 150      2000    182       78     Changed Chart                                                                 Paper                                       165      2000    192       95                                                 180 (3 hr)                                                                             2000    196      101                                                 188      2000    190      102     Start Cool-                                                                   Down                                        195        0     189      105                                                 210        0     189      109                                                 225        0     189      113                                                 240 (4 hr)                                                                               0     189      119                                                 255        0     189      122                                                 270        0     189      122                                                 285        0     189      122                                                 300 (5 hr)                                                                               0     189      125                                                 315        0     182      122                                                 330        0     178      121                                                 345        0     166      121                                                 360 (6 hr)                                                                               0     162      120                                                 375        0     152      113                                                 ______________________________________                                    

EXAMPLE 17 & COMPARATIVE EXAMPLE 5

The shearing strength of the fly ash blocks of Example 16 wasdetermined. This was compared to the shearing strength of slump blockswhich were bonded using Portland Cement Mortar (Comparative Example 5).The fly ash blocks were bonded using a fly ash mortar composition whichhad the same fly ash:bottom ash ratio as the block. The loading wasapplied to an assembly of 4 blocks vertically, which were bonded usingthree joints. The loading was applied to the blocks while they wereoriented with the mortar joints parallel to the direction of loading.The two outside blocks were supported on the underside by wooden spacershaving a width and length which fully supported each block. The loadingwas applied across the full width of the center two blocks, imposingshear loading on two mortar joints. The keyed section of the fly ashblocks was oriented in the vertical direction.

The results are shown in table 3.

TABLE 3 Example 17

Bonded Surface area of each joint: 147.26 square inches

Applied loading: 9,220 lbs

Shearing stress: 31.3 psi

Comparative Example 5

Bonded Surface area of each joint: 60 square inches

Applied loading: 2,900 lbs

Shearing stress: 24.1 psi

EXAMPLE 18

The effect of delay in undertaking the compression step of the presentinvention was observed. 33% by weight C-grade fly ash, 33% by weightbottom ash; and 33% by weight wood ash (waste product) were mixedtogether to form a dry mixture. Water was added to this dry mixture inan amount of 14% by weight. The resulting blended mixture was formedinto four blocks, by placing successive amounts of the blended mixtureinto a press box, and compressing the material under a 1750 psi maximumload. The formation of the bricks was conducted at an ambienttemperature of 72° F. The compressive strength of each block wasdetermined, and the plots of this test are shown in FIGS. 8 to 11, forblocks 1 to 4 respectively.

Block 1 was compressed approximately 1 minute after the dry mixture wasblended with water. Block 2 was compressed approximately 2 and 1/2 to 3minutes after mixing with water. Block 3 was compressed approximately 5to 6 minutes after blending with water. Block 4 was blended 9 to 10minutes after blending with water.

It was found that the compressive strength of the blocks increased whenthe mixture was subjected to a longer setting time in the magazinehopper, prior to compression into the brick. This is of course, limitedby the fact that excessive delay (much more than 10 minutes) will allowthe material to quickset, and will result in a non-usable powderymaterial. The results of this test are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                        Block    Set time (min)                                                                            Compressive Strength (psi)                               ______________________________________                                        1        1           3050                                                     2        2.5-3       3143                                                     3        5-6         3232                                                     4        8-9         3462                                                     ______________________________________                                    

What is claimed:
 1. A construction block prepared by:(a) blending a drymaterial with water, wherein said dry material comprises a materialselected from the group consisting of volcanic fly ash and kiln dust;(b) transferring the blended material to a compression zone, which issized such that it contains an amount of blended material to produce aconstruction block; and (c) compressing the blended material at apressure of 1000 to 2500 psi to form the construction block.
 2. Aconstruction block prepared by:(a) blending a dry material with water,wherein the dry material comprises a mixture of aggregate and a materialselected from the group consisting of kiln dust and volcanic fly ash;(b) transferring the blended material to a compression zone, which issized such that it contains an amount of blended material to produce aconstruction block; and (c) compressing the blended material at apressure of 1000 to 2500 psi to form the construction block.
 3. Aconstruction block according to claim 1 or 2, said block possessing aridge on a face of the block, and a groove a different face of theblock, wherein the face containing the groove is located on the oppositeside of the block from the face with the ridge;wherein the ridge islocated in the center of the face, and extends the full length of centeraxis of the block, and the groove is substantially identical in shape tothe ridge, and is located in substantially the same relative orientationon the face opposite to that which the ridge is located on, further,said block contains a pair of small grooves in the face containing theridge, said small grooves being oriented perpendicularly to the ridge,and running from the edge of the block to the ridge, and one of each ofsaid small grooves being located on opposite sides of the ridge.
 4. Aconstruction block according to claim 1 or 2, said block possessing tworidges on a face of the block, and two grooves on a different face ofthe block, wherein the face containing the grooves is located on theopposite side of the block from the face with the ridge;wherein a firstridge is located on the center axis of the face, and extendsapproximately 1/2 the length of the center axis of the block, and asecond ridge is located in said face and is oriented perpendicularly tothe first ridge, the second ridge extending from one edge of the bricksubstantially to the other edge of the bridge, and being locateapproximately half way between the end of the first ridge and the end ofthe block,wherein the grooves are substantially identical in shape tothe ridges, and are located in substantially the same relativeorientation on the face opposite to that which the ridge is located on,further, said block contains a pair of small grooves in the facecontaining the ridge, said small grooves being oriented perpendicularlyto the first ridge, and running from the edge of the block to the ridge,and one of each of said small grooves being located on opposite sides ofthe ridge.
 5. The construction block according to claim 2, wherein theaggregate includes shard glass.
 6. A construction block prepared by:(a)blending a dry material with water, wherein the dry material comprises amixture of volcanic fly ash or kiln dust and an additive comprisinglime, gypsum plaster, polymers, pumice, clay, or aggregate; (b)transferring the blended material to a compression zone, which is sizedsuch that it contains an amount of blended material to produce aconstruction block; and (c) compressing the blended material at apressure of 1000 to 2500 psi to form the construction block.
 7. Theconstruction block according to claim 6, wherein said additive ispresent in an amount greater than zero and up to 20% by volume of thetotal dry composition.
 8. A construction block prepared by:(a) blendinga dry material with water, wherein the dry material comprises a mixtureof volcanic ash or kiln dust and a hazardous material to be encapsulatedin the construction block; (b) transferring the blended material to acompression zone, which is sized such that it contains an amount ofblended material to produce a construction block; and (c) compressingthe blended material at a pressure of 1000 to 2500 psi to form theconstruction block.
 9. The construction block according to claim 8,wherein the hazardous material comprises asbestos, contaminated soils,pesticides, herbicides, petroleum waste products, PCB contaminants, lowyield radioactive waste, acids, medical ash, municipal solid wastes,incinerator ash, or gasification plant ash.
 10. A construction blockprepared by:(a) blending a dry material with water, wherein the drymaterial comprises a mixture of volcanic ash or kiln dust and ahazardous material to be encapsulated in the construction, block,wherein the hazardous material is low yield radioactive waste; (b)transferring the blended material to a compression zone, which is sizedsuch that it contains an amount of blended material to produce aconstruction block; (c) compressing the blended material at a pressureof 1000 to 2500 psi to form the construction block; (d) heating acomposition which contains a material selected from the group consistingof kiln dust and volcanic fly ash to a temperature sufficient to liquifythe composition; and (e) dipping the construction block into theliquified composition, so as to provide a glass coating on the exteriorsurface of the construction block.
 11. The construction block accordingto claim 2, wherein the dry material contains kiln dust and the weightratio of kiln dust to aggregate is in the range 15% kiln dust : 85%aggregate to 100% kiln dust : 0% aggregate.
 12. The construction blockaccording to claim 11, wherein the ratio of kiln dust to aggregate is50:50.
 13. The construction block according to claim 11 wherein saidcompression step is achieved using a compression ram.
 14. Theconstruction block according to claim 11, wherein the amount of wateradded to the dry material to form the blended material is in the rangeof 10 to 20% by weight relative to the total weight of the dry material.15. The construction block according to claim 14, wherein the amount ofwater added to the dry material is in the range 13 to 15% by weightrelative to the total weight of the dry material.
 16. The constructionblock according to claim 15 wherein the amount of water added to the drymaterial is 14% by weight of the dry material.
 17. A construction blockprepared by:(a) forming a dry composition comprising aggregate and a drymaterial selected from the group consisting of kiln dust and volcanicfly ash, wherein the dry material to aggregate ratio is in the range 15%dry material : 85% aggregate to 100% dry material : 0% aggregate, byweight; (b) blending the dry composition with water, which is added inan amount which is approximately 14% by weight relative to the totalweight of the dry composition; (c) transferring the blended compositionto a press box, wherein the amount of blended composition which istransferred into the press box is dependent on the size of the blockwhich is to be formed, and the press box is sized so as to contain thecorrect amount of blended composition which is needed in order toproduce a construction block; and (d) compressing the blended mixture ata pressure of 1500 to 2500 psi in the press box in order to form theconstruction block.
 18. The construction block according to claim 2,wherein the dry material comprises volcanic fly ash, and the weightratio of volcanic fly ash to aggregate is in the range 15% volcanic flyash : 85% aggregate to 100% volcanic fly ash : 0% aggregate.
 19. Theconstruction block according to claim 18, wherein the ratio of volcanicfly ash to aggregate is 50:50.